The present invention relates to an x-ray measuring technique, and more particularly to an x-ray measuring apparatus which performs tomography on a subject using x-rays.
X-ray measuring apparatuses (hereinafter referred to as CT apparatuses) are used for performing rotation image acquisition during the rotation of an x-ray source and a one-dimensional x-ray detector around the subject, using the one-dimensional x-ray detector. Another type of x-ray measuring apparatuses (hereinafter referred to as cone-beam CT apparatuses) are also used for performing rotation image acquisition during the rotation of an x-ray source and a two-dimensional x-ray detector around the subject, using the two-dimensional x-ray detector. CT apparatuses and cone-beam CT apparatuses are used for performing rotation image acquisition during the rotation of the subject, using a fixed x-ray source and a fixed x-ray detector. These CT apparatuses and cone-beam CT apparatuses are well-know techniques.
In the CT apparatuses and cone-beam CT apparatuses, a set of projection data for three-dimensional reconstructing processing is obtained through correction of a plurality of measurement data acquired by the rotation image acquisition. A three-dimensional image is obtained by three-dimensional reconstructing the obtained projection data, using a three-dimensional reconstruction algorithm. A well-known cone-beam CT reconstruction algorithm includes a Feldkamp method, etc. Such reconstruction algorithms are widely known.
A two-dimensional x-ray detector used in the cone-beam CT may be an I.I.-camera-type x-ray detector or a flat-type x-ray detector, etc. The I.I.-camera-type x-ray detector is a combination of an I.I. (Image Intensifier) and a video camera through an optical system. In the flat-type x-ray detector, sets of an amorphous silicon diode and a TFT are arranged in a square matrix, and these sets and a fluorescent screen are combined in direct. These sensors are well-known techniques.
U.S. Pat. No. 5,493,593 suggests a CT apparatus and a reconstruction process capable of reconstructing a tomographic image in a larger view angle than that of a detector. In this conventional CT apparatus, a one-dimensional detector is displaced in a direction parallel to the plane of rotation generated by an x-ray source and the detector. The detector is placed on one side of a straight line passing through the x-ray source and the rotation center of the x-ray source, and perform photographing. The detector executes a reconstruction process using the one side data of the obtained projection data. In this configuration, non-redundant projection data can be obtained, the photography view is extended along the plane of x-ray source rotation, and the field of view of a reconstructed image can be extended. In this CT apparatus, the extension of the photography view can approximately be double.
Japanese Patent Application Laid-Open No. 11-9583 suggests a cone-beam CP apparatus and a reconstruction process capable of reconstructing a tomographic image in a larger view angle than that of a detector. In this conventional cone-beam CT apparatus, a two-dimensional detector is displaced along the plane of rotation generated by an x-ray source and the detector. The detector is placed on one side of a straight line passing through the x-ray source and the rotation center of the x-ray source, and perform photographing. The obtained projection data is divided in a part corresponding to the axis of rotation of the two-dimensional detector, and a reconstruction process is carried out using one of the divided data. In this configuration, non-redundant projection data can be obtained, the photography view is extended along the plane of x-ray source rotation, and the view of a reconstructed image can be extended. In this cone-beam CT apparatus, the extension of the photography view can approximately be double.